1. Field of Invention
This invention relates to precision cutting of discrete devices such as, for example, ink jet printheads and, more particularly, to a resinoid/diamond dicing blade further including a dry lubricant used for said precision cutting. The present invention further relates to a method of making the blade, and a method of using such a blade for precision cutting operations.
2. Description of Related Art
There are many discrete devices that are generally formed as a plurality of substrates integrally formed in a wafer or the like, and which require intermediate cuts and/or separation into individual subunits as a last step in the fabrication process. Examples of such discrete devices are ink jet printheads, magnetic heads, and semiconductor sensor devices. Most, but not all, of the devices are formed in silicon-based wafers. A preferred technique for separating the subunits is to saw through the wafer in a procedure referred to as xe2x80x9cdicing.xe2x80x9d In such dicing operations, the device used to perform the cutting is referred to as a dicing blade or dicing saw. For cutting operations requiring high precision, such as +/xe2x88x920.5 micron, resinoid/diamond blades have been preferred, especially in the production of thermal ink jet printheads, because they form precisely placed, smooth, chipless cuts.
According to the prior art, resinoid/diamond blades have been typically constructed of a resin-diamond blend. For example, a resinoid/diamond blade is disclosed in U.S. Pat. No. 4,878,992, which is constructed of a relatively hard, dense resin bonded material and a 60 to 90% concentration of natural or synthetic diamonds. Other resinoid/diamond blades and their use are disclosed in U.S. Pat. Nos. 5,160,403, 5,266,528 and 4,851,371.
U.S. Pat. No. 5,160,403 discloses a method of fabricating a semiconductor device having a buttable edge from a first wafer having first and second opposite planar surfaces and a second wafer having first and second opposite planar surfaces. A first component is formed on the first planar surface of the first wafer. A precision dice cut is placed in the first planar surface of the first wafer closely adjacent to the first component. The precision dice cut extends partially through the first surface of the first wafer and defines the buttable edge. The first surface of the first wafer is bonded to the first surface of the second wafer, the first surface of the second wafer containing a second component and being aligned with and bonded to the first wafer so that the first and second components cooperate to form the semiconductor device. Portions of the first and second wafers surrounding the first and second components, respectively, are then removed to define the semiconductor device. The step of removing can include placing a second dice cut entirely through the first and second wafers parallel to and slightly offset from the precision dice cut. The second dice cut being located slightly further away from the first component than the precision dice cut and intersects a portion of the precision dice cut so that a side of the semiconductor device that includes the buttable edge is defined by the precision dice cut and the second dice cut.
U.S. Pat. No. 5,266,528 discloses a method of dicing a semiconductor wafer for dividing a semiconductor wafer having a large number of devices formed thereon in a matrix into a large number of chips by the use of a diamond blade. The method includes the steps of first cutting by the use of the diamond blade in such a manner as to leave a partial residual portion or portions in a direction of thickness of the wafer and to define a plurality of grooves on the wafer in transverse and longitudinal directions, and then cutting the wafer along the grooves by the use of a resin blade having a width equal to or smaller than that of the diamond blade while a feed speed thereof is kept lower than that of the diamond blade. U.S. Pat. No. 4,851,371 discloses a method of fabricating a large array or pagewidth silicon device having high resolution. The pagewidth device is assembled by abutting silicon device sub-units such as image sensors or thermal ink jet printheads. For printheads, the sub-units are fully operational small printheads comprising an ink flow directing channel plate and a heating element plate, which are bonded together. A plurality of individual printhead sub-units are obtained by dicing aligned and bonded channel wafers and heating element wafers. The abutting edges of the printhead sub-units are diced in such a manner that the resulting kerfs have vertical to inwardly directed sides, which enable high tolerance linear abutment of adjacent sub-units. Alternatively, the wafer surface containing the heating elements is first anisotropically etched to form small V-grooves, one wall of which protects against microcracking during the dicing operation. The other wall of the V-groove is obliterated by the slanted dicing blade.
Despite the recent improvements in dicing blade manufacture, the above-described resinoid/diamond blades still suffer from performance variability, generally manifested in wearing down of the blade cutting edge and asymmetric wear of the blade periphery. The dicing blades also generally suffer from shortened blade life due to chipping caused by the forces generated when pieces of silicon or diamond particles loosened from the dicing blade become jammed between the rotating dicing blade and the silicon wafers being cut. The use of natural or synthetic diamonds also adds to the expense.
Several improvements on the known dicing blades have been suggested as means to improve the accuracy and economics of the dicing operations. For example, U.S. Pat. No. 5,637,388 discloses a composite resinoid/graphite/diamond blade having enhanced precision cutting properties. The blade is made by assembling several layers, each layer comprising a veil of non-woven graphite fabric of fibers having an outside diameter of 10 microns, impregnated with a mixture of diamond particles blended into a phenolic resin. The diamond content of the blades was in the order of 100-120% (100%=72 carats/cubic inch). Layers are built up in sandwich fashion. In one described embodiment, four layers are formed and, in a heating compression molding operation, the sandwich is compressed into a composite blade having a diameter of 4.7 inches with a thickness of 0.011 inch. The final blade is formed by a die cut and lapping process. The layered construction is described to yield a blade with more consistent cross-section and improved blade wear symmetry. In another described embodiment, the layers are tailored to have a grit concentration of the diamond/resin mixture at the periphery or cutting edge.
Furthermore, in U.S. Pat. No. 5,494,698 there is disclosed a resinoid/diamond dicing blade having approximately a 20% by volume porosity structure. The structure is coated and impregnated with Teflon(copyright) by a process that impregnates the resinoid/diamond blade with Teflon(copyright) to about 0.3 to 0.5% by weight. The Teflon(copyright) impregnated dicing blade is described to not only reduce nozzle chipping when bonded silicon wafers are separated into a plurality of individual printhead die, but blade life is significantly increased.
Various dicing operations and methods are also known in the art, as described in the above-referenced patents. In addition, U.S. Pat. No. 4,878,992 describes an ink jet printhead fabrication process wherein a plurality of printheads are produced from two mated substrates by two dicing operations. One dicing operation produces the nozzle face for each of a plurality of printheads and optionally produces the nozzles. This dicing blade, together with specific operating parameters, prevent the nozzles from chipping and the nozzle faces from scratches and abrasions. A second dicing operation with a standard dicing blade severs the mated substrates into separate printheads. The dicing operation which produces the nozzle face is preferably conducted in a two-step operation. A first cut makes the nozzle face, but does not sever the two mated substrates. A second dicing cut severs the two substrates, but does so in a manner that prevents contact by the dicing blade with the nozzle face.
However, a need continues to exist in the ink jet art, and in the semiconductor art in general, for improved dicing blades and dicing operations that provide more precise cuts and more economical dicing processes.
Thus, in embodiments of this invention, the present invention provides a composite resinoid/diamond dicing blade, comprising diamond particles and a dry lubricant dispersed in a resin binder. In other embodiments, the present invention also provides a method of cutting a substrate using a dicing blade, comprising cutting a substrate using the disclosed dicing blade, as well as a method of making such a dicing blade, comprising: providing a mixture of resin, diamond particles, and a dry lubricant; and forming said mixture into a dicing blade.